1. Field of the invention.
The present invention relates to a shearmachine for preferentially fly-cutting with high speed of advancing bars and more particularly to the composition of said machine with parallel and/or shear-units with alternating combined action. Both the grouping of shears of this type as well as the respective installations form the object of the present invention, which is particularly useful for the high speed cutting of bars or like products of lamination.
2. Description of The Prior Art.
The shears for rolled products in use at the present time, which consist generally of two rotating knives, present obvious limitations as far as the cutting speed is concerned.
The fact is well known that the shearing is assured by way of two knives, rotating in opposite directions, and the cuttingspeed of these knives at the cutting instant equals the forward speed of the bar at the instant of the cutting itself.
With each cut of the knives, the machine produces a bar of the desired length. It is evident that with this method the knives have in one turn to start from the beginning, accelerate to the exit speed of the laminated bar, cut the bar, decelerate and stop at the position where the cycle begins, in the vertical point over the cutting area.
The accelerations and the decelerations take place in an angular space, not more than 180.degree., since at the utmost, a half turn is used for the deceleration and a half turn for the acceleration, but in reality, the spaces for deceleration and acceleration do normally not exceed 150.degree. - 160.degree., and it is evident, that for a certain distance the knives have to rotate in the cutting area at a constant speed. Because of the limited spaces allowed for the acceleration and the deceleration, these machines have to be constructed in a very strong way. However this massive construction creates a greater inertness, and therefor the speed can not be increased, unless the knife supports are not lightened. The gears and all the elements in movement are to compromise the consistency of the machine itself.
Since it is not conveniently possible to increase the acceleration and the deceleration of the knives, which are already at their limits, the problem of the high cutting speed can only be solved by increasing the acceleration space, which is impossible with the present cutting system, because the angle of the turn for the knife is completely taken up, at the utmost half of it for the acceleration and half of it for the deceleration.